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John C.Briggs, Professor Emeritus, Department of Fisheries and Wildlife, Oregon State University, Corvallis, OR
97333, USA

(29 June 2015)

Is a Sixth Global Mass Extinction Underway?

John C. Briggs*
In their recent article, published in Sciences Advances, Ceballos et al. (19 June 2015) endeavored to demonstrate that species extinctions by humans have caused the world to enter into its sixth mass extinction. As evidence, they compared extinction rates, among terrestrial vertebrates for the past few centuries, to the historical rate from the geological record. However, the historical rate was calculated only from data on mammal extinctions. The authors assumed that the historical mammal rate could be applied to all the other vertebrates (birds, reptiles, amphibians, and fishes). Using the mammal data, the authors determined that, without human influence, only nine vertebrate extinctions would have been expected since the year 1900.
According to the Red List (IUCN, 2014), 198 extinctions were recorded for all terrestrial vertebrates since the year 1900. Compared to the expected nine extinctions during that time (Caballos et al., 2015), an increase of 189 appears to indicate a disastrous human influence. Extending back to the year 1500, a total of 338 were documented by the Red List. In addition to these numbers, the authors recognized 279 more species under “extinct in the wild” and “possibly extinct” categories. These figures produced a grand total 617 vertebrate species lost or presumed lost since 1500. These impressive numbers persuaded...

John C. Briggs*
In their recent article, published in Sciences Advances, Ceballos et al. (19 June 2015) endeavored to demonstrate that species extinctions by humans have caused the world to enter into its sixth mass extinction. As evidence, they compared extinction rates, among terrestrial vertebrates for the past few centuries, to the historical rate from the geological record. However, the historical rate was calculated only from data on mammal extinctions. The authors assumed that the historical mammal rate could be applied to all the other vertebrates (birds, reptiles, amphibians, and fishes). Using the mammal data, the authors determined that, without human influence, only nine vertebrate extinctions would have been expected since the year 1900.
According to the Red List (IUCN, 2014), 198 extinctions were recorded for all terrestrial vertebrates since the year 1900. Compared to the expected nine extinctions during that time (Caballos et al., 2015), an increase of 189 appears to indicate a disastrous human influence. Extending back to the year 1500, a total of 338 were documented by the Red List. In addition to these numbers, the authors recognized 279 more species under “extinct in the wild” and “possibly extinct” categories. These figures produced a grand total 617 vertebrate species lost or presumed lost since 1500. These impressive numbers persuaded the authors to declare that the evidence is “incontrovertible”, that the recent extinction rates are unprecedented, and that the rate is highly unusual in Earth history. Therefore, they concluded that a mass extinction episode had been initiated.
The unfortunate aspect of this work is that no reference was made to other estimates of global extinctions using other faunal groups. Extinctions recorded in the marine environment were not considered, and no mention was made about concurrent gains in species diversity. About 90% of the terrestrial world’s species are insects. A recent estimate by an entomologist (Dunn, 2005) indicates a species diversity of about 3.4 million. While many insect species are still undescribed, certain groups, (butterflies, tiger beetles, dragonflies, and damselflies) are well known and their extinctions during the past 500 years have been documented. Within those groups, which total 25,260 species, only two species have become extinct (Briggs, 2014). In the marine environment, which covers about 71% of the Earth’s surface, the diversity of multicellular species is about 2.21 million (Mora et al., 2011); of this number, only 20 have been recorded to be extinct (Dulvy et al., 2009). Furthermore, a recent, uncited paleontological work on extinctions (MacLeod, 2013) provides valuable information on Pleistocene and modern extinction rates. Finally, there is good evidence that points to continual gains in diversity due to species invasions and rapid ecological speciation (Briggs, 2014).
Aside from the neglect of the published information cited above, the attempt to forecast a global extinction on the basis of only terrestrial vertebrate animals (Ceballos et al., 2015), is unconvincing when comparable information on other faunal groups is not utilized. Also, in dealing with the numbers of vertebrate extinctions, the authors failed to mention that most of them took place on oceanic islands. In regard to the mammals and birds, more than 95% of all extinctions during the past 500 years were island species (Loehle and Eschenbach, 2012). If we use the mammals and birds as surrogates for all the vertebrates, extinctions on the world’s continents must have been very low. For example, only three of the 61 mammal extinctions took place on continents. The loss of isolated island species had little or no effect on continental ecology.
This is the latest in a series of books and papers, published over the past 40 years, devoted to the frightening vision of a human-caused mass extinction. Its use of colorful graphs, showing vertebrate species dying off by the hundreds, presents a doomsday scenario that many are likely to believe, unless they consider the global extinction evidence.
References
Briggs, J.C. (2014) Global biodiversity gain is concurrent with declining population sizes. Biodiversity Journal, 5, 447-452.
Ceballos, G., Ehrlich, P.R., Barnosky, A.D., García, A., Pringle, R.M. & Palmer, T.M. (2015) Accelerated modern human-induced species losses: entering the sixth mass extinction. Science Advances. 1:e 1400253.
Dulvy, N.K., Pinnegar, J.K., & Reynolds, J.D. (2009) Holocene extinctions in the sea. In: Turvey, S.T. (Ed.) Holocene extinctions. Oxford University Press, Oxford, pp. 129-150.
Dunn, R.R. (2005) Modern insect extinctions: the neglected majority. Conservation Biology, 19, 1030-1036.
IUCN (2014) www.iucnredlist.org (March 20, 2015).
Loehle, C. & Eschenbach, W. (2012) Historic bird and terrestrial mammal extinction: rates and causes. Diversity and Distribution, 18, 84-91.
MacLeod, N. (2013) The great extinctions. Firefly Books, Buffalo, NY.
Mora, C., Tittensor, D.P., Adl, S., Simpson, A.G.B. & Worm, B. (2011) How many species are there on Earth and in the ocean? PLoS Biol. 9, e21001127.
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*Department of Fisheries and Wildlife, Oregon State University, Corvallis, OR 97333, USA; e-mail: clingfishes@yahoo.com Current address: 2320 Guerneville Rd., Santa Rosa, CA 95403,

Is human species who considered himself at the pedestal of superiority is inviting its own end? This is suggested in the present study by Ceballos et al. where they attempted to identify the next mass extinction. The pace at which species are getting extinct is alarming. Though there were reports earlier about the high rate of extinction of species in post industrialization era, yet lack of conclusive parameters and estimates always diluted the effect it should have on the policy makers and public. Comparison of “highly conservative modern extinction rate” and “background extinction rate” in this study provides a clear picture of rapid extinction of species. Man’s consumerist approach has been responsible for bringing on the possibility of sixth mass extinction that could very well have been avoided by adopting small measures in light of knowledge of ecology and modern science.
Various anthropogenic factors like deforestation, aggressive exploitation of natural resources, mining and mindless dumping toxic wastes in natural environment may have plausible role for massive extinction. While we are trying to explore life on other planets, forgetting to concentrate to take measures to save our own planet. Man has lost the touch with nature and has become oblivious of his role of just a co-habitant on Earth not its master. Small steps like supporting the local animals and birds and separating solid wastes can go a long way in this direction. If we learn to appreciate t...

Is human species who considered himself at the pedestal of superiority is inviting its own end? This is suggested in the present study by Ceballos et al. where they attempted to identify the next mass extinction. The pace at which species are getting extinct is alarming. Though there were reports earlier about the high rate of extinction of species in post industrialization era, yet lack of conclusive parameters and estimates always diluted the effect it should have on the policy makers and public. Comparison of “highly conservative modern extinction rate” and “background extinction rate” in this study provides a clear picture of rapid extinction of species. Man’s consumerist approach has been responsible for bringing on the possibility of sixth mass extinction that could very well have been avoided by adopting small measures in light of knowledge of ecology and modern science.
Various anthropogenic factors like deforestation, aggressive exploitation of natural resources, mining and mindless dumping toxic wastes in natural environment may have plausible role for massive extinction. While we are trying to explore life on other planets, forgetting to concentrate to take measures to save our own planet. Man has lost the touch with nature and has become oblivious of his role of just a co-habitant on Earth not its master. Small steps like supporting the local animals and birds and separating solid wastes can go a long way in this direction. If we learn to appreciate the role of biodiversity for our well being, progress and future survival and found ways to nurture and conserve it in a sustainable manner, we can at least delay the mass extinction if not avoid it.
Consortium development and effective data collection and further analysis will lead to more awareness about the issue and conservation at global scale.

The article brings some interesting statistics showing the increase rate of extinctions among mammal and vertebrate. The over population of humans is obviously a great problem and has been for years. The population of humans in the early 1960s was around 3 billion and today over 7 billion and projected to be around 10 billion by 2020. No matter what mankind does that kind of overpopulation will put a stress on earth's ecosystems and animals and bio-systems. I remember scientists in the 1970s warning of overpopulation.. it is the fundamental basis for all the environmental problems. This article, if the stats are correct, bring this more to light.
However this article's very important point looses credibility with statements like: "All of these are related to human population size and growth, which increases consumption (especially among the rich), and economic inequity". Over population increases consumption - period. Consumption of resources is world wide and is effected by population increases world wide, not just the rich ( and I assume you meant rich countries). And population increases are happening more rapidly in the less "rich" countries. "Overexploitation for economic gain" is minor compared to just the sheer volume of people living on the earth that consume air and food and resources and create waste. The destruction of the rain forest in South America since the 1940s to make cheap farming land for the poor has probab...

The article brings some interesting statistics showing the increase rate of extinctions among mammal and vertebrate. The over population of humans is obviously a great problem and has been for years. The population of humans in the early 1960s was around 3 billion and today over 7 billion and projected to be around 10 billion by 2020. No matter what mankind does that kind of overpopulation will put a stress on earth's ecosystems and animals and bio-systems. I remember scientists in the 1970s warning of overpopulation.. it is the fundamental basis for all the environmental problems. This article, if the stats are correct, bring this more to light.
However this article's very important point looses credibility with statements like: "All of these are related to human population size and growth, which increases consumption (especially among the rich), and economic inequity". Over population increases consumption - period. Consumption of resources is world wide and is effected by population increases world wide, not just the rich ( and I assume you meant rich countries). And population increases are happening more rapidly in the less "rich" countries. "Overexploitation for economic gain" is minor compared to just the sheer volume of people living on the earth that consume air and food and resources and create waste. The destruction of the rain forest in South America since the 1940s to make cheap farming land for the poor has probably done as much damage to species extinction as other factors. That rain forest is huge role in photosynthesis as well as maintaining millions of animal lives.
While this article is important in its statistics on animal extinctions, it barely touches on how the loss directly is caused by man or effects man or any solutions (which I understand that is not what this article was for). The article ended sounding of some sort of opinionated agenda which lessen its scientific credibility. Still very important.